110 Megakaryopoiesis and Thrombopoiesis

Question 1

The circulatory lifespan of a platelet

• Normal platelet counts:
• Moderate thrombocytopenia:
• Severe thrombocytopenia:

Answer 1

• Normal platelet counts:10 days
• Moderate thrombocytopenia: 7 days
• Severe thrombocytopenia: 5 days

Question 2

Approximate number of megakaryocytre and platelets produced per day

Answer 2

Platelet: 1 × 10^11 platelets per day
Megakaryocyte:1 × 10^8 megakaryocytes per day

If one megakaryocyte produces approximately 1000 platelets

Question 3

The transit time from megakaryocyte progenitor cell to release of platelets into the circulation ranges from

Answer 3

4–7 days

Question 4

An integral transmembrane protein of two subunits, with the α subunit being megakaryocyte-lineage specific

Answer 4

Integrin αIIbβ3

Absence of integrin αIIbβ3 leads to Glanzmann thrombasthenia

Question 5

The second most abundant megakaryocyte-specific protein

Answer 5

Glycoprotein (GP) Ib-IX complex

Question 6

Caused by homozygous or complex heterozygous mutation of the gene encoding the thrombopoietin receptor c-MPL, leading to a near absence of megakaryocytic progenitors and megakaryoblasts and platelet levels approximately 10% of normal

Answer 6

Congenital amegakaryocytic thrombocytopenia

Question 7

Acts in synergy with thrombopoietin to enhance megakaryocyte production

Answer 7

Stem cell factor (SCF)

Question 8

The cytokine that can induce growth of marrow progenitors into colonies containing immature megakaryocytes in vitro in the absence of thrombopoietin

Answer 8

Interleukin-3 (IL-3)

Question 9

A transcription factor vital for committing primitive multipotent progenitors to the erythroid–megakaryocyte pathway, and also critical later in megakaryopoiesis for cytoplasmic development

Answer 9

GATA-1

Question 10

The primary regulator of megakaryocyte maturation

Answer 10

Thrombopoietin